1. Field of the Invention
This invention relates to a socket in which contacts are shifted backwardly by an operating member so that the contacts are moved away from a circuit element. The term "circuit element" used herein refers to an element which forms a circuit.
2. Brief Description of the Prior Art
According to the invention discussed in Japanese Patent Early Laid-Open Publication No. Hei 4-154065, contacts arranged in rows are engaged with a swing lever, so that when the swing lever is swung, the contacts can be shifted, as a group, backwardly away from leads of an electric part in order to facilitate zero-force insertion of the electric part.
However, this prior art has the problem that when the contacts are shifted backwardly upon operation of the swing lever, or when the contacts are shifted forwardly by elasticity of the contacts, a vertical contact pressure is difficult to obtain efficiently because a contacting portion of each contact is brought into contact with or moved away from an upper surface of each lead at a comparatively small angle of inclination. As a result, reliability of contact is lowered.
Recently, there has been a tendency that miniaturization of the contacts has increased and elasticity has been lowered, so that a proper contact pressure is increasingly difficult to obtain. A solution to this problem is required. Furthermore, since the contacting portion of each contact is brought closer to the upper surface of each lead from a location away from the lead at a low angle, there is the risk that the contacting portion will collide with the leading end of each lead owing to a manufacturing error, causing turning-up or warping of the leading end of each lead, etc.